To analyse by single-crystal x-ray diffraction analysis the observed structures of psychoactive substances including neuroleptics, the tricyclic anti-depressants, and narcotic analgesics; to consider the possible conformations other than those observed, to correlate the conformations with each other and with pharmacodynamic pharmacological activity to provide a unifying theory for any one class of pharmacologically active substances of three-dimensional structure activity relationships showing the conformation and pharmacodynamic groups required for such activity.